Sean Farley, a bear researcher and wildlife physiologist with the
Alaska Department of Fish and Game, emphasized that bear spray has
proven hugely effective on charging bears, especially charging
grizzlies.

But he noted the physical state of those bears. They charge with eyes
wide open, nostrils flaring and often huffing air into their lungs.
They are fully exposed to the active ingredient in the spray – oleoresin
capsicum, an oily extract from the pepper plant.
Unlike tear gas, which appears to work poorly on bears, capsicum
causes more than just irritation to the eyes. Inhaled, it inflames
airways making it temporarily harder to breathe and from what is known
about research on humans, it might do even more than that.

A charging grizzly is likely to get a big dose of capsicum.
That is not necessarily the case for a predatory bear. . . . Farley describes predatory bears as approaching with eyes squinting,
mouths shut and nostrils narrowed. They come in like bears approaching
beehives ready to suffer a bit to get the food they want. Their physical
preparations would serve to minimize the dose of spray hitting the
bear.

The post goes on to talk about risk-assessment: "Statistically, you are orders of magnitude more likely to die in a motor
vehicle or boating accident in Alaska than to be attacked by a bear,
let alone killed by one." But fear of bears is more primal than fear of motorboats.

And there is speculation on the changing nature of predators world-wide. Read it all.

The big about bears approaching beehives reminded me of when my late brother-in-law was raising hogs on his farm in southeastern Missouri. His was a small operation, maybe a dozen or so at a time, partly for the family and partly for sale.

He told me about one particular hog that would bust through an electric fence. The pig knew that it would get shocked, so it started squealing before it hit the fence, but it still wanted to break through more than it did not want to be shocked. There is no reason why some bear might not take the same attitude toward bear spray.

I still carry it at appropriate times, however. It also works well on overly aggressive dogs. And I see that Medred still carries it too.